Hi, I have a 53 Chevy with airbag in the rear and am working on rewiring the power for the compressors but I'm a little confused on the ignition switch. The plastic indicator says Lock, Off, On, Start. I think this is the stock trim for the 53 Chevy ignition switch but I suspect it has a universal ignition switch. When I turn counterclockwise (in the lock position) the compressor can turn on and I also hear the external fuel pump turn on. In the center (Off) it behaves as I expect, nothing is on. The first right clockwise click (On) lets the compressor and external fuel pump turn on. The following click starts the car up (Start). It it has a universal switch that doesn't match the plastic indicator. If the left counterclockwise click is accessory, I'm not sure why the external fuel pump turns on. Basically I'm trying to make it so I can run my compressors prior to starting the car. If they are running and I try to crank at the same time, I often blow the fuse at the fuse box for the power line running to the compressors. My other idea is to install a manual toggle switch and leave the compressors off until the car is started and running. Usually the compressors don't turn on unless the car is sitting for a couple weeks, meaning it has a really minimal leak. I had fellow HAMBer SpecialEd help me check the airlines, fitting, etc. and we got the leak to be really minimal.
Sounds like your compressors and fuel pump are wired to the acc terminal. The solution to the blown fuses is to use a separate switch for the compressors and leave them off while starting.
Thanks! Yea that sounds even better for the compressor that way I can turn it on/off any time I want independent of the key. I wonder why the fuel pump would be wired to the acc terminal? It also turns on in the ON position. I'm guessing someone wired it wrong and I need to make sure it's not connected on the acc just to have it set up properly?
It was probably wired to the accesories terminal so the carb could be primed up after sitting for a while. That way you get gas into the carb without having to crank the bejesus out of the motor. I have a similar sett up on a Caddy , but I just have a push ****on switch under the dash.
Thanks. I remember the previous owner telling me it's easier to start it if I let the fuel pump run for a little while prior to cranking it. So should I leave the ignition wiring alone and when it's sitting for a week or more, turn it to the Accessories for a couple minutes and then turn it to ON then crank it? I have noticed when it sits for a couple of weeks I have to crank it a few times.
You don't mention relays in your comments. The compressors are a fairly high amp draw item and they should be supplied by a relay to avoid the load going through the switch contacts. By using a relay, only the light current load of the relay goes through the switch but it still controls the circuit. Ray
I would leave the fuel pump wired as, and maybe run the compressor through a relay and a seperate switch as mentioned. You will hear the pumps "note" change when the needle closes on the seat in the carby , should only take a few seconds.
Chevrolets through the 50s and into the 60s had a unique ignition switch in that the face of the switch was a knob that could be turned without a key, meaning the engine could be started, stopped and run without needing the key. The only purpose the key served was to put the ignition switch in or out of the lock position and once in the lock position the switch could not be turned without unlocking with the key. There was no accessory position. You definitely have a universal ignition switch. Depending on how many connectors you have on the switch you may have options on how to wire. The simplest of universal switches will have 4 connectors, battery, accessory, ignition, and start. In this case the accessory wire will be hot in both accessory and run positions. You'll have to look at the back of the switch to verify exactly what you have. Typically all accessory connectors will be hot in the run position, switches with multiple accessory connections however some of the connectiors might not be hot when in the crank position and others just might not be hot in the run position. And typically all ignition terminals are hot in the run position, switches with multiple ignition connections however some of the connectors may only be hot in the crank position. You could wire the fuel pump and compressor and nothing else to the accessory side if you wanted to run them before starting.
Good call. The upper limit current-wise on any of the aftermarket key switches is usually 30 amps total connected load, and any motor-driven device (fuel pump, compressor) can easily have inrush current of 300% or more of it's running current. I'd use a relay for any motor-driven device, and size the relay at 150% of the running current for reliability.
I'm going to get underneath with a multimeter and check the wiring. How long should it typically take to prime the carb if I run the fuel pump in ACC mode and its been sitting a couple of weeks? Is there a quick way to determine if the ACC mode is turning the ignition components on? I just want to verify they aren't wired up to the ACC as well. Thanks.
Fuel pump should slow down when float bowl is filled. 10 seconds max. Test light, properly grounded. You can use a needle pushed in to the wire or connector to give a bare metal place to touch tip, but use caution and DO NOT let the pin touch a ground. They get red hot quickly. Just so you know, the key switch normally sends power to different input wires of a fuse panel (or panels) for switched or accessory side circuits. Power in from lugs on switch, thru fuse, out to component. One important note is that circuits powered off ACC side should go OFF temporarily while switch is in START position. IGN lug will stay hot while in START position.
Best quick way is to put a test light on the positive side of the coil with the switch in the accessory position. And since there are many different ways a universal ignition switch might work if you really want to know what terminal is hot in which key position you will need to disconnect the wires to the switch and use an ohm meter. Then put one lead on the switch's battery connector and then check resistance to every other connector with the key in every position on each. And write it down so you'll remember in the future.
Great thanks! Is it bad to prime the carb for 10 seconds in the ON position? I'm guessing I should do it on the ACC side as 36roadster suggested.
The test at positive side of coil should also be done in IGN position and START position. Coil must be getting voltage in both of those positions. ACC voltage typically goes off when key is turned to START position, to maximize voltage during starter engagement. Be sure voltage to coil does not go off when key is turned to START position. Voltage is restored to ACC pole after key returns to IGN. The issue with priming carb (running fuel pump) for 10 with IGN on probably won't matter UNLESS you have a distributor with points which will pit over time. Fuel pump could easily be connected to a fused circuit powered by ACC side of switch.
Thanks, the car starts up fine so the switch works as I expect. On the ACC position, the fuel pump turns on. It has an HEI distributor with pertronix (according to the previous owner). In this case am I better off priming the carb in the ACC position?
If you have an electronic ignition, there will be no points to burn out, so it doesn't matter which position you prime it in.
Thanks, I'll add a switch for the compressor and take off the fuel pump from the ACC side since I can prime the carb in the ON position.
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